What Is 5G?
AT&T, Verizon, and other carriers will start to launch 5G networks this year. But what exactly is 5G, and how fast is it compared with 4G? Here's what we know so far.
Sascha Segan Icon
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Sascha Segan
March 20, 2018 4:35PM EST
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 5G
5G Is Real
At the end of 2017, the wireless industry came up with the first official 5G standard. AT&T plans to launch mobile 5G in the US this year, Verizon says it will launch 5G for homes, and both T-Mobile and Sprint say that they're launching 5G phones early next year.

But a standard doesn't mean that all 5G will work the same—or that we even know what applications 5G will enable. There will be slow but responsive 5G, and fast 5G with limited coverage. Let us take you down the 5G rabbit hole to give you a picture of what the upcoming 5G world will be like.

1G, 2G, 3G, 4G, 5G
The G in 5G means it's a generation of wireless technology. While most generations have technically been defined by their data transmission speeds, each has also been marked by a break in encoding methods, or "air interfaces," which make it incompatible with the previous generation.

1G was analog cellular. 2G technologies, such as CDMA, GSM, and TDMA, were the first generation of digital cellular technologies. 3G technologies, such as EVDO, HSPA, and UMTS, brought speeds from 200kbps to a few megabits per second. 4G technologies, such as WiMAX and LTE, were the next incompatible leap forward, and they are now scaling up to hundreds of megabits and even gigabit-level speeds.

5G brings three new aspects to the table: greater speed (to move more data), lower latency (to be more responsive), and the ability to connect a lot more devices at once (for sensors and smart devices).

The actual 5G radio system, known as 5G-NR, won't be compatible with 4G. But all 5G devices, initially, will need 4G because they'll lean on it to make initial connections before trading up to 5G where it's available.

4G will continue to improve with time, as well. The upcoming Qualcomm X20 modem will support 4G speeds up to 2Gbps. The real advantages of 5G will come in massive capacity and low latency, beyond the levels 4G technologies can achieve.

That symbiosis between 4G and 5G has caused AT&T to get a little overenthusiastic about its 4G network. The carrier has started to call its 4G network "5G Evolution," because it sees improving 4G as a major step to 5G. It's right, of course. But the phrasing is designed to confuse less-informed consumers into thinking 5G Evolution is 5G, when it isn't.

How 5G Works
Like other cellular networks, 5G networks use a system of cell sites that divide their territory into sectors and send encoded data through radio waves. Each cell site must be connected to a network backbone, whether through a wired or wireless backhaul connection.

5G networks will use a type of encoding called OFDM, which is similar to the encoding that 4G LTE uses. The air interface will be designed for much lower latency and greater flexibility than LTE, though.

The standard will work all the way from low frequencies to high, but it gets the most benefit over 4G at higher frequencies. 5G may also transmit data over the unlicensed frequencies currently used for Wi-Fi, without conflicting with existing Wi-Fi networks. That's similar to a technology that all the carriers except Sprint are currently launching, called LAA.

5G networks are much more likely to be networks of small cells, even down to the size of home routers, than to be huge towers radiating great distances. Some of that is because of the nature of the frequencies used, but a lot of that is to expand network capacity. The more cells you have, the more data you can get into the network.

So 5G networks need to be much smarter than previous systems, as they're juggling many more, smaller cells that can change size and shape. But even with existing macro cells, Qualcomm says 5G will be able to boost capacity by four times over current systems by leveraging wider bandwidths and advanced antenna technologies.

The goal is to have far higher speeds available, and far higher capacity per sector, at far lower latency than 4G. The standards bodies involved are aiming at 20Gbps speeds and 1ms latency, at which point very interesting things begin to happen.

Who's Launching 5G When?
AT&T has proclaimed that it will be first with mobile 5G when it launches a network in 12 cities by the end of this year. While it hasn't given details, we think this will be "millimeter wave" 5G, which requires dense networks of cells that don't reach very far (say, about 1000 feet each), but deliver extremely high speeds.

AT&T's rollout could be slowed by a lack of 5G phones available before 2019, though. Qualcomm has said that 5G phones will be available in 2019, but not before then. AT&T said in early February that it would launch not with phones, but with a "puck" that observers are assuming is a mobile hotspot.

Verizon is starting out with a fixed 5G home internet service launching in three to five cities in mid 2018. Sacramento will be the first city. This will use home routers with fixed antennas that Verizon will be able to supply, getting around the pesky phone problem. Presumably, this will offer gigabit internet to compete with local cable companies, but you won't be able to tote it around.

5G home internet shows one major advantage over 4G: huge capacity. Carriers can't offer competitively priced 4G home internet because there just isn't enough capacity on 4G cell sites for the 190GB of monthly usage most homes now expect. This could really increase home internet competition in the US, where, according to a 2016 FCC report, 51 percent of Americans only have one option for 25Mbps or higher home internet service. For its part, Verizon told us there wouldn't be 4G-level data caps on home 5G service.

5G home internet is also much easier for carriers to roll out than house-by-house fiber optic lines. Rather than digging up every street, carriers just have to install fiber optics to a cell site every few blocks, and then give customers wireless modems.

T-Mobile is taking yet another approach. The company is building a nationwide 5G network on the 600MHz band starting in 2019, with full national coverage by 2020. The low-band network will be supplemented by millimeter wave in large cities, which is the sort of 5G AT&T and Verizon are building out.

The speed of a wireless network is tied to how much spectrum you can use for it. Because T-Mobile is only using an average of 31MHz of spectrum at 600MHz as opposed to the hundreds of MHz that millimeter wave networks will use, its low-band 5G network will be a little bit faster than 4G, but not multiple gigabits fast. It will still have the low latency and many connections aspects of 5G, making it usable for gaming, self-driving cars, and smart cities, for instance. In cities, the millimeter-wave network will be super-fast.

"Are we going to see average speeds start to move up by tens of megabits per second? For sure," T-Mobile CTO Neville Ray said. "We would love to see average speeds triple, or move to 100Mbps, but that's a journey that's going to take time in the industry."

Sprint is preparing to launch 5G smartphones early next year, potentially at Mobile World Congress in February, the company's CTO said. Sprint's 5G will be on the 2.5GHz band, which will give it similar coverage to Sprint's existing 4G LTE network; in fact, it will use the same cell sites.

While reports recently surfaced of a federally owned nationwide 5G network, they were quickly shut down by the FCC.

Watch: Oulu Tech: Long-Hackathon
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What's 5G For?
So Verizon wants to use 5G as a home internet service, and everybody else is more focused on faster smartphones. Those are only the initial uses of a network that can connect everything to everything else.

On a trip to Oulu, Finland, where they have a 5G development center, we attended a 5G hackathon (see the video above). The top ideas included a game streaming service; a way to do stroke rehab through VR; smart bandages that track your healing; and a way for parents to interact with babies who are stuck in incubators. All of these ideas need either the high bandwidth, low latency, or low-power-low-cost aspects of 5G.

Driverless cars may need 5G to really kick into action, our editor Oliver Rist explained after CES this year. The first generation of driverless cars will be self-contained, but future generations will interact with other cars and smart roads to improve safety and manage traffic. Basically, everything on the road will be talking to everything else.


Honda self-driving car
To do this, you need extremely low latencies. While the cars are all exchanging very small packets of information, they need to do so almost instantly. That's where 5G's sub-one-millisecond latency comes into play, when a packet of data shoots directly between two cars, or bounces from a car to a small cell on a lamppost to another car. (One light-millisecond is about 186 miles, so most of that 1ms latency is still processing time.)

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Another aspect of 5G is that it will connect many more devices. Right now, 4G modules are expensive, power-consuming, and demand complicated service plans, so much of the Internet of Things has stuck with Wi-Fi and other home technologies for consumers, or 2G for businesses. 5G networks will accept small, inexpensive, low-power devices, so it'll connect a lot of smaller objects and different kinds of ambient sensors to the internet.

What about phones? The biggest change 5G may bring is in virtual and augmented reality. As phones transform into devices meant to be used with VR headsets, the very low latency and consistent speeds of 5G will give you an internet-augmented world, if and when you want it. The small cell aspects of 5G may also help with in-building coverage, as it encourages every home router to become a cell site.

We're looking forward to testing the first implementations of 5G as soon as they are live. Every year we drive around the country evaluating network speeds for our Fastest Mobile Networks feature, and as 5G rolls out, the results are sure to get more interesting—and exciting—than ever before.